Search for double beta decay of ${}^{136}$Ce and ${}^{138}$Ce with HPGe gamma detector

Abstract

Search for double ${\hat{I}}^2$ decay of ${}^{136}$Ce and ${}^{138}$Ce was realized with 732 g of deeply purified cerium oxide sample measured over 1900 h with the help of an ultra-low background HPGe ${\hat{I}}^3$ detector with a volume of 465 cm${}^3$ at the STELLA facility of the Gran Sasso National Laboratories of the INFN (Italy). New improved half-life limits on double beta processes in the cerium isotopes were set at the level of $\lim T_{1/2}\sim 10^{17}-10^{18}$~yr; many of them are even two orders of magnitude larger than the best previous results.

21 pages, 6 figures, 3 tables; version accepted for publication on Nucl. Phys. A